An aneurysm is a blood-filled dilation of a blood vessel. Major concerns with aneurysms revolve around rupturing of the arterial wall causing internal bleeding and clots breaking away from the aneurysm causing strokes.
There exist two generally approved methods of treating aneurysms. The first method of treatment includes surgical treatment. The second method of treatment includes endovascular treatment. Surgical removal of the aneurysm is sometimes not possible, leaving endovascular treatment as the only available option. Even when not the only option, endovascular treatment often is preferred because of the reduced risks and complications.
Conventionally, endovascular treatment of an aneurysm involves “packing” the aneurysm such that an endovascular occlusion is formed. Packing the aneurysm with coils, such as Guglielmi Detachable Coils (or GDCs), helps form an occlusion. While using GDCs is conventional, the aneurysm can be packed with numerous devices, such as, for example, other types of coils, balloons, glues, polymers, clotting agents, liners, or the like. Recent studies have found, however, that the body breaks down conventional treatments re-exposing blood flow to the aneurysm.
Endovascular treatment, while considered less risky than surgical treatment, has other drawbacks as well. One drawback of endovascular treatment of the aneurysm includes the potential to over pack the aneurysm. Over packing the aneurysm can cause the material to enter the parent blood vessel, potentially altering blood flow in the remaining vessel or generating undesirable pressure in the aneurysm. Also, some aneurysms have a wide connection to the blood vessel, a.k.a. wide neck aneurysms. Wide neck aneurysms have the additional risk that the occluded material will break free of the aneurysm and enter the parent blood vessel, potentially causing blockage of the parent blood vessel. Finally, clotting agents and polymers used to form occlusions in the aneurysm can seep to the parent blood vessel causing complications. Balloons and liners are intuitively pleasing as a solution, but have the potential for an inexact fit causing complications. For example, a balloon may be over inflated causing unwanted pressure or under inflated causing seepage in the aneurysm.
While the packing methods described above alter blood flow to the aneurysm, the aneurysm neck typically is open to the parent blood vessel. Thus, blood continues to flow to the aneurysm. To reduce the blood flow, several devices have been developed to cover the neck area of the aneurysm.
U.S. Pat. No. 6,454,780, issued Sep. 24, 2002, to Wallace, titled Aneurysm Neck Obstruction Device, shows a device designed to cover or block the neck of the aneurysm. FIG. 1 shows the Wallace device 10 in some detail. The device 10 is placed inside aneurysm 50 using a catheter 46 and deployment tool 44. When inside the aneurysm 50, device 10 has walls 12 that expand or unfold to contact the inside of the aneurysm 50 and block neck 51. But the device resides internal to aneurysm 50 allowing blood flow shown by arrow A in the parent vessel 52 to push up against the walls 12. The upward pressure of the blood vessel on the wall 12 may allow blood from the parent vessel to seep in aneurysm 50. Also, because the wall is internal to the aneurysm 50, the neck 12 has the potential to expand. Other types of internal devices include liners and other neck bridges.
Devices to block the neck of the aneurysm external to the aneurysm exist also. These devices use the pressure of the blood vessel to help seat the block against the parent vessel wall and shield the neck from the blood vessel. One such device is shown in U.S. Pat. No. 6,309,367, issued Oct. 30, 2001, to Boock, titled Aneurysm Shield. The Boock device is shown in FIG. 2. The Boock device 30 has a cylindrical shaft 32 that covers the neck 37 of the aneurysm 38 and is anchored by anchor rings 34 and 36. While device 30 resides external to the aneurysm it has multiple parts that could break free or deteriorate that reside in the parent vessel. While the Boock device 30 seemingly works for its intended purpose in theory, its relatively large size and surface area makes its impractical to actually use. In the brain, for example, multiple blood vessels may branch off from the location of an aneurysm. Attempting to use the Boock device would block blood flow to one or more of the branch vessels as well as the aneurysm, which makes the Boock device useful in only limited situations, if any.
Thus, it would be desirous to develop and improve internal and external aneurysm stents. Further, it would be desirous to develop a device capable of delivering growth factor to the aneurysm neck to promote aneurysm neck occlusion.